Searching for “LiCr{sup II}PO{sub 4}”

Journal Article · Wed Oct 15 04:00:00 EDT 2014 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2014.06.020· OSTI ID:22443421

Mosymow, E. ^[1]; Kremer, R. K. ^[2]

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1. Institut für Anorganische Chemie, Universität Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn (Germany)
2. Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart (Germany)

The two new phosphates LiCr{sup II}{sub 4}(PO{sub 4}){sub 3} and Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4} are discovered as equilibrium phases (ϑ=800 °C) in the quarternary system Li/Cr/P/O. Their crystal structures have been determined from single-crystal X-ray diffraction data (LiCr{sup II}{sub 4}(PO{sub 4}){sub 3}: violet-blue, Pnma (no. 62), Z=4, a=6.175(1) Å, b=14.316(3) Å, c=10.277(2) Å, 100 parameters, R{sub 1}=0.028, wR{sub 2}=0.08, 2060 unique reflections with F{sub o}>4σ(F{sub o}); Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4}: greyish-green, P1{sup ¯} (no. 2), Z=1, a=4.9379(7) Å, b=7.917(2) Å, c=8.426(2) Å, α=109.98(2)°, β=90.71(1)°, γ=104.91(1)°, 131 parameters, R{sub 1}=0.022, wR{sub 2}=0.067, 1594 unique reflections with F{sub o}>4σ(F{sub o})). Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4} adopts an hitherto unknown structure type. The crystal structure of LiCr{sup II}{sub 4}(PO{sub 4}){sub 3} is isotypic to that of NaCd{sup II}{sub 4}(PO{sub 4}){sub 3} and related to that of the mineral silicocarnotite Ca{sub 5}(PO{sub 4}){sub 2}(SiO{sub 4}). Significant disorder between Li{sup +} and Cr{sup 2+} is observed for both crystal structures. The oxidation states assigned to chromium in these two phosphates are in agreement with UV/vis/NIR absorption spectra and magnetic susceptibility data recorded for both compounds. Instead of “LiCr{sup II}PO{sub 4}” mixtures of LiCr{sup II}{sub 4}(PO{sub 4}){sub 3}, Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4}, Cr{sub 2}O{sub 3}, and CrP are observed at equilibrium. Instead of “Li{sub 2}Cr{sup II}P{sub 2}O{sub 7}” four-phase mixtures consisting of Li{sub 9}Cr{sup III}{sub 3}(P{sub 2}O{sub 7}){sub 3}(PO{sub 4}){sub 2}, Li{sub 3}Cr{sup III}{sub 2}(PO{sub 4}){sub 3}, LiCrP{sub 2}O{sub 7}, and CrP were obtained. - Graphical abstract: Investigations on the equilibrium relations in the system Li/Cr/P/O revealed the two hitherto unknown phosphates Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4} and LiCr{sup II}{sub 4}(PO{sub 4}){sub 3}. They form instead of “LiCr{sup II}PO{sub 4}”. The crystal structures, magnetic behavior and optical spectra of these phosphates are reported. - Highlights: • The two new phosphates Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4} and LiCr{sup II}{sub 4}(PO{sub 4}){sub 3} have been characterized. • Optical spectra and paramagnetism of the these phosphates are explained by AOM. • Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4}, LiCr{sup II}{sub 4}(PO{sub 4}){sub 3}, Cr{sub 2}O{sub 3}, and CrP occur instead of “LiCr{sup II}PO{sub 4}”. • LiCr{sup II}{sub 4}(PO{sub 4}){sub 3} is structurally closely related to Silicocarnotite Ca{sub 5}(PO{sub 4}){sub 2}(SiO{sub 4}). • Li{sub 5}Cr{sup II}{sub 2}Cr{sup III}(PO{sub 4}){sub 4} and LiCr{sup II}{sub 4}(PO{sub 4}){sub 3} exhibit significant cation disorder Li{sup +}/Cr{sup 2+}.

• OSTI ID: 22443421
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 218; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTRA
CATHODES
CATIONS
CHROMATES
CHROMIUM IONS
LITHIUM IONS
MAGNETIC SUSCEPTIBILITY
MIXTURES
MONOCRYSTALS
ORTHORHOMBIC LATTICES
PARAMAGNETISM
PHOSPHATES
REFLECTION
SILICATES
SILICON OXIDES
SIMULATION
SOLIDS
SPECTROSCOPY
SYNTHESIS
X-RAY DIFFRACTION